The present invention relates to a high pressure fuel supply pump, and particularly, to a high pressure fuel supply pump suitable for feeding under pressure high pressure fuel to a fuel injection valve of an internal combustion engine.
Further, the invention relates to a high-pressure fuel supply pump provided with a variable capacity mechanism for adjusting quantity of fuel discharged.
{circle around (1)} In a conventional high pressure fuel supply pump, for example, as shown in Japanese Patent No. 2690734 Specification, fuel is supplied from a tank to a high pressure pump by a low pressure pump to increase its pressure to high, and is supplied to a common rail. Within the high pressure pump, an intake passage and a discharge passage are communicated with an upper end surface of a pressurizing chamber and an intermediate side wall of the pressurizing chamber, respectively.
Further, in the other conventional high pressure fuel supply pump, for example, as shown in Japanese Patent Application Laid-Open No. Hei10-318091 Publication, an intake passage and a discharge passage are communicated with an intermediate side wall or an upper end surface of a pressurizing chamber and an upper end surface of the pressurizing chamber, respectively.
Incidentally, when the engine is first started, or restarted after stoppage for a long period, vapor of air or fuel is present within a fuel pipe. Therefore, immediately after start, the pressure increasing characteristic of the high pressure pump is apt to be deteriorated. To prevent this, it is necessary to rapidly discharge air or fuel vapor within the pressurizing chamber of the high pressure pump to thereby secure the pressure increasing characteristic of the high pressure pump, and to rapidly supply fuel into the common rail by a low pressure pump of large discharge capacity.
However, in the high pressure fuel supply pump described in Japanese Patent No. 2690734 Specification, an intake passage and a discharge passage are provided on an upper end surface of a pressurizing chamber and an intermediate side wall of the pressurizing chamber, respectively, thus posing a problem in that in the intake stroke, vapor or the like is hard to be discharged on the intake passage side due to the intake fuel, and in the discharge stroke, the vapor or the like is apt to remain within the pressurizing chamber above the discharge passage, thereby lowering the supply property of fuel.
Also in the constitution described in FIG. 5 of Japanese Patent Application Laid-Open No. Hei10-318091 Publication, a discharge passage within the high pressure pump is provided in an upper end of a pressurizing chamber, and therefore, vapor within the pressurizing chamber is apt to be discharged. However, both the above-described prior arts have a problem in that since fuel fed from the low pressure pump is communicated with the pressurizing chamber which changes in volume due to piston motion within the high pressure pump, even if an attempt is made to supply fuel to the common rail by the low pressure pump immediately after the engine starts, the piston motion within the pressurizing chamber makes resistance to delay a supply of fuel.
Further, in the conventional constitution described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei10-318091 Publication, since an upper flat surface of a cylinder fixing portion is compressed and fitted, fuel flows into the outer periphery of a delivery valve passing through the outer circumference of a cylinder when the intake passage is communicated with the intermediate side wall of the pressurizing chamber, because of which, an O-ring is provided for sealing from outside. However, this poses a problem in that when an O-ring is formed from an elastic member, it moves due to the pressure variation in the pressuring chamber, and therefore, pressure rising of the pressurizing chamber reduces, or rubbing wear or rupture of the O-ring occurs.
{circle around (2)} Further, with respect to a seal mechanism against a leakage of high pressure fuel, in the conventional high pressure fuel supply pump, fuel in the pressurizing chamber is increased to high pressure by reciprocating movement of a plunger. Here, since fuel pressure pressurized is considerably high pressure, fuel possibly leaks out of a clearance between the plunger and the cylinder.
In view of the foregoing, in the conventional high pressure fuel supply pump, a seal material of an elastic member is disposed on the end of a sliding portion of a plunger, as described in Japanese Patent Application Laid-Open No. Hei 10-318068 Publication and Japanese Patent Application Laid-Open No. Hei8-368370 Publication, to prevent a leakage of fuel. On the fuel chamber side of the seal material is provided with a passage communicated with a fuel tank which is substantially at atmospheric pressure. Further, a sliding portion of the plunger is provided therein with a fuel reservoir leading to a fuel intake port which is a low pressure portion. By the provision of these constitutions noted above, when one end of the seal material is in contact with the atmospheric pressure, the other end is also communicated with the fuel tank to be substantially atmospheric pressure so as not to apply high pressure of the pressurizing chamber onto the seal material directly, thus preventing a leakage of fuel from the seal material.
However, the high pressure fuel supply pump described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei 10-318068 Publication poses a problem in that since the distance from the fuel reservoir (a pulsation reducing space in FIG. 1) in communication with the low pressure fuel chamber to the sliding end of the plunger is short, when the seal material is broken or fallen off, a large quantity of fuel possibly flows outside from a clearance of the plunger sliding portion.
On the other hand, in the high pressure fuel supply pump described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei 8-368370 Publication, since the distance from the fuel reservoir (a sliding hole 11a of a cylinder 11 in FIG. 1) in communication with the low pressure fuel chamber to the sliding end of the plunger is long, it is possible to make small the quantity of fuel which flows out when the seal material is broken or fallen off. However, since the sliding distance of the plunger from the pressurizing chamber to the fuel reservoir cannot be made long, thus posing a problem in that when pressurized, fuel leaks into the low pressure portion from a clearance of the sliding portion of the plunder to deteriorate the discharge efficiency.
Further, in the high pressure fuel supply pump described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei 8-368370 Publication, the distance from the pressurizing chamber to the fuel reservoir is prolonged to thereby enable prevention of a leakage of fuel, but it is necessary, to this end, to prolong the full length of the sliding portion, thus posing a problem in that the whole pump becomes large in size.
Further, in the conventional high pressure fuel supply pumps described in Japanese Patent Application Laid-Open No. Hei 10-318068 and No. Hei 8-368370, since both ends of the seal material are made substantially at atmospheric pressure, it is necessary to provide, on the fuel chamber side of the seal material, a passage in communication with the fuel tank substantially at atmospheric pressure, thus making it necessary to have a passage for connecting the pump to the fuel tank. As a result, there was a problem in that processing of a pump becomes complicated, and a piping for connecting the pump to the tank is necessary, thus increasing the cost.
{circle around (3)} Next, with respect to the variable capacity mechanism, an apparatus heretofore known has the constitution wherein, for example, as described in Japanese Patent No. 2690734, an electromagnetic valve is provided within an intake passage, and a returning quantity to the intake side is controlled by opening and closing operation of the electromagnetic valve to thereby adjust the discharge quantity.
Further, the constitution is known for example, from Japanese Patent Application Laid-Open No. Hei 10-153157, wherein a check valve is provided within an intake passage, and a spill (overflow) valve is provided in a fuel spill (overflow) passage in communication with a pressurizing chamber whereby quantity of fuel spill to a fuel tank is controlled by opening and closing the spill valve to thereby adjust the discharge quantity.
Since rotation of a pump increases by a multiple of a cam of the pump with respect to the number of revolutions of the engine, it is necessary to open and close the intake valve or the spill valve in order of msec (millisecond). However, in such a state of high speed opening and closing, mass of the electromagnetic valve influences on the respondence.
A first object of the present invention is to provide a high pressure fuel supply pump capable of enhancing fuel supply property to a common rail immediately after start of an engine.
A second object of the present invention is to provide a high pressure fuel supply pump capable of enhancing pressure increasing property to a common rail immediately after start of an engine.
A third object of the present invention is to provide a high pressure fuel supply pump which suppresses an external leakage of fuel to a small quantity, even when a seal material of a sliding portion is broken or fallen off, and which is small in size and cheap.
A fourth object of the present invention is to provide a high pressure fuel supply pump having a variable capacity mechanism which is excellent in opening and closing respondence.
(1) For achieving the aforementioned first object, the present invention provides a high pressure fuel supply pump for pressurizing fuel supplied from an intake passage of fuel by a pressurizing member to feed it under pressure to a discharge passage, wherein in addition to a main pressurizing chamber in which said pressurizing member is arranged, a sub-pressurizing chamber for communication between said intake passage and said discharge passage is provided.
With the above constitution, fuel supplied from an intake passage by a low pressure pump can be supplied to a common rail via a discharge passage without being impeded by resistance caused by motion of a pressurizing member of a high pressure pump, thus enabling enhancement of fuel supply property to the common rail.
(2) In the above-described (1), preferably, said intake passage and said discharge passage are placed in communication with an upper end portion of said pressurizing chamber.
With the above constitution, in the discharge stroke, discharging of air and fuel vapor in the pressurizing chamber can be carried out securely, and a dead volume of the pressurizing chamber (a volume of the pressurizing chamber at the top dead center) can be minimized without impairing a fuel supply to the pressurizing chamber, thus enabling miniaturization of the high pressure pump.
(3) In the above-described (1), preferably, said sub-pressurizing chamber is arranged substantially annularly on the outer periphery of said main pressurizing chamber.
(4) For achieving the aforementioned second object, the present invention provides a high pressure fuel supply pump for pressurizing fuel supplied from an intake passage of fuel by a pressurizing member to feed it under pressure to a discharge passage, comprising a pressurizing chamber forming member having a tapered surface on the end and formed from a member separately from a pump body, said tapered surface of the pressurizing chamber forming member being compressed and fitted by a fixing member to thereby form said pressurizing chamber.
With the above constitution, the pressurizing chamber forming member can be fixed without providing an elastic member such as rubber, thus enabling enhancement of pressure increasing property to the common rail.
(5) For achieving the aforementioned third object, the present invention provides a high pressure fuel supply pump having an intake passage of fuel, a pressurizing chamber in communication with a discharge passage, and a pressurizing member for feeding under pressure fuel within said pressurizing chamber to said discharge passage, comprising: a seal material arranged on a sliding portion of said pressurizing member, a connecting passage for communicating the fuel chamber side of said seal material with the intake passage of fuel, and a check valve for impeding entry of fuel into said seal material side from said fuel intake passage side.
With the aforementioned constitution, even if the seal material is broken or the like, a leakage of fuel due to the check valve can be prevented, and by providing no portion in communication with the atmospheric, miniaturization and reduction in cost can be achieved.
(6) In the aforementioned (5), preferably, said check valve is opened when operation of a pump is stopped.
With the above constitution, it is possible to prevent the check valve when the pump is stopped from being adhered to the seat surface.
(7) In the aforementioned (6), preferably, said check valve is formed from an elastic member.
(8) The fourth object of the present invention is achieved by providing a high pressure pump comprising a valve body for opening and closing a fuel through-hole provided between a cylinder and a low pressure side passage, a spring for biasing said valve body in a closing direction with respect to said through-hole, an operating rod in contact with or spaced from said valve body to adjust opening and closing timing of said valve body, and an electromagnetic mechanism for driving the operating rod electromagnetically in association with the operating condition of the internal combustion engine.
In the present invention constructed as described above, since mass of the valve body will not be a load with respect to the electromagnetic driving mechanism, the respondence of the discharge capacity control mechanism is improved.
(9) In the aforementioned (8), the electromagnetic driving mechanism can be used in common with the intake valve mechanism.
(10) In the aforementioned (8), the electromagnetic driving mechanism can be constituted as a spill (overflow) valve mechanism.
(11) Further, preferred embodiments of the present invention are as follows:
An intake valve is provided on the intake passage, and to the intake valve is applied a small biasing force in a closing direction to a degree that automatically opens when fuel flows into the pressurizing chamber. Further, an engaging member having a biasing force for holding in an opening direction is engaged with the intake valve, and the engaging member controls the intake valve to open and close according to operating timing of an actuator.
Thereby, in the intake stroke of the pump, the intake valve can be opened irrespective of the operation of the actuator. Also in the compression stroke, since the intake valve maintains its open state unless the actuator is operated (ON), surplus fuel in the pressurizing chamber reduced as a result of the compression is returned to the intake side. Accordingly, since pressure of the pressurizing chamber is not risen, fuel is not fed under pressure to the discharge passage. In this state, when the actuator is operated (ON), the intake valve is closed by self-closing force so that pressure of the pressurizing chamber increases and the fuel is fed under pressure to the discharge passage. In this manner, the discharge quantity can be adjusted by controlling the operating timing of the actuator.
Upon maximum discharging, the ON state of the actuator is maintained whereby the intake valve is automatically opened and closed in synchronism with pressure of the pressurizing chamber, and therefore, the maximum discharge can be carried out without depending on the respondence of the actuator.
Further, upon low discharging, the actuator is turned ON from the latter half of the compression stroke and turned OFF till the termination of the intake stroke, and therefore, the high respondence is not necessary.
Furthermore, at the time of discharge, only the intake valve is required to close, and therefore, a leakage of fuel from the seat can be reduced.
(12) Preferably, if an electromagnetic type actuator is employed, control can be made simply by an engine control unit. Further, a fuel injection valve can also be used for the actuator.
(13) Further, preferably, an engaging portion between an intake valve and an engaging member is made in the form of a concavo-convex engagement, whereby deviation, slipping out or the like of the engaging portion can be prevented to secure positive operation.
(14) Further, preferably, a ball valve is used for the intake vale or the discharge valve, whereby the processing accuracy of the seat portion can be readily enhanced. Further, a cylindrical member is engaged with the ball valve, and the outer circumference of the cylindrical member is held capable of being reciprocated and slidably moved within the intake passage, so that the oscillation of the ball valve can be prevented. Further, since the cylindrical member is separated from the ball valve, both of them can be fabricated in an easy method.
(15) Further, preferably, in a plunger reciprocating and sliding type pump, a sliding portion of a plunger is made to be a cylindrical member separately from a pump body, whereby only the sliding member can be formed of a material suitable for sliding movement. Further, an inner wall of the cylindrical member is formed with a sliding hole of a plunger and an expanded inner wall portion having a larger inside diameter than the former, and only the outer peripheral portion of the diffused inner wall can be pressed and fitted in the pump body whereby preventing the sliding hole from being deformed. Accordingly, it is not necessary to re-process the sliding hole after fitting the cylindrical member, enabling fabrication at low cost.
(16) Further, preferably, a clearance is provided at a position other than the portion in which the cylindrical member is fitted in the pump body, an annular passage is formed on the outer peripheral portion of the cylindrical member, and the annular passage is made to communicate with one end of the plunger sliding hole and a fuel introducing passage, whereby fuel introducing pressure is guided into the annular passage to reduce a pressure difference relative to the pressurizing chamber, and thus enabling reduction in leakage quantity of fuel when passing through the fitting portion and the sliding portion from the pressurizing chamber. Further, since the fuel covers the outer circumference of the sliding portion, it is possible to cool the sliding portion.
(17) Moreover, preferably, a member in engagement with the pump body and the cylindrical member is provided in the fuel passage whereby the cylindrical member can be prevented from falling off while preventing a leakage of fuel from the engaging portion to the outside the pump or occurrence thereof.